Signal Loss after Sunking

[bigp7099]

I built a buffered sunking and have been very happy sounds really good, happy couple of months. I finished a run off groove thor yesterday and tried it out, also very nice, worked great going direct into my amp. I added it into my board after the sunking and hey where did all the tone go? turned on the sunking and it sounded really good but wasn't quite what i expected, nowhere near the drive. I then took out the sunking and the thor sounded like it did when i had it going directly into the amp, put the sunking after it same thing, turned them both on - that's what i was expecting (way too much basically). is the buffer in my sunking screwed up? all i have is delay and modulation after the drive portion and i never noticed that the sunking was affecting those pedals, i didn't have time to pull everything off my board last night and test exactly what was happening i guess that's tonight's project.

any thoughts, i searched here but didn't find anything that seems relevant.

[bigp7099]

so i took it out of the board and it's pretty obvious wherever i put the sunking when it's off it's killing the signal going through. i pretty much only played with it on before so i guess i just never noticed. any suggestions? i guess i should just open it up and start checking pin voltages.

[oldhousescott]

Which revision of the Sunking did you build? There was an issue with earlier versions wrt the bypass switching in the way certain resistors were placed in the circuit.

[bigp7099]

version 3 maybe i should check that as well though

[CRBMoA]

V.3 Bypass resistors are switch mounted. 2 x 68K and 1 x 100k, mounted on the switch.

It should look something like this: [clickable thumbs]

[jkokura]

Yeah, the switch wiring sounds like the issue. If I remember right that was an experience others had around the same time.

Jacob

[bigp7099]

i have the resistors on the switch, i wonder if any of them are grounding out on my shielding, or would that just kill the signal entirely

[jkokura]

Not likely. If the leads were grounding then yes, but the bodies themselves shouldn't matter.

But I do think you need to investigate your bypass wiring. I remember specifically that the phenomenon you're describing to be precisely the issue we are indicating.

Jacob

[bigp7099]

thanks i'll definitely be checking that out

[bigp7099]

well i don't think it is the resistors on the switch but i'll take the whole thing apart and check that as well as the pin voltages

[bigp7099]

well i'm stumped - the resistors on the switch all are good as far as i can tell, i checked the pin voltages and i got 2 that are off IC1-3 is 1.08 and IC3-7 is 3.66, everything else is pretty close - does anybody know if there are pin voltages i should be checking with the effect bypassed though as that is when i am having the problem.

should i start this again in another part of the forum?

[jkokura]

I don't know if it has to do with the resistors so much as the wiring. Could you post some good pictures of your current switch and wiring to and from the board?

Jacob

[oldhousescott]

Those two pin readings are probably OK. The meter will load the circuit at IC1-3 causing a low reading. IC3-7 is the oscillator pin, so I doubt you'll get any usable reading on it.

Keep after it, you gotta be getting close.

[bigp7099]

Here is a pic with notes

[oldhousescott]

It's hard to tell for sure from the pics, but it looks like R30, the resistor spanning pins 2 and 5 on your switch, is brown-black-brown which would be only 100 ohms, instead of brown-black-yellow for 100k. If indeed it's a 100 ohm in there, that would cause a severe signal drop due to the voltage divider created by R4 (or R24) and R30.